1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing a long molding having at least one of an axial bend and an axial twist along a longitudinal direction in which a long second member is integrated with a long first member. The method and apparatus of the invention are preferably applied to the long molding in which the second member made of a resin molding material is integrated overhanging (projecting) from the first member. Also, the method and apparatus of the invention are preferably applied to the long molding in which the cross sectional shape of the second member (e.g., extent of overhang from the first member) is different between one part and the other part in the longitudinal direction.
2. Background Art
Long moldings are well known in which the long second member is integrated with the long first member. Some of the long moldings have one of the axial line bent at a predetermined radius of curvature and the axial line twisted at least in one part in the longitudinal direction. Examples of the long molding having the at least one of bend and twist (hereinafter generically referred to as a “bend”) include a long trim member attached along the body edge of the vehicle, and fittings attached along the edge of a building having a curved surface structure.
One example of the trim member is a pillar and roof molding (hereinafter simply referred to as a “pillar molding”) attached continuously from a front pillar portion of the vehicle to a roof portion along a bend on a corner portion between the pillar portion and the roof portion, in which the axial line is bent like the “L” character in an attached state, as seen from the lateral face of the vehicle. The axial line of this pillarmolding is typically formed in such a way that a part from the corner portion to the lower end of the pillar portion is twisted compared with the roof portion with reference to the carriage in the roof portion. This twist is required because the lateral face of the vehicle is like a spindle shape (or a beer cask), and the pillar molding is placed out of the parallel or perpendicular direction to the central axis of the spindle shape.
The pillar molding of typical shape comprises a long main portion (first member) extruded from a first molding material and having a head portion like a flat plate, and a concealing portion (second member) projecting from near one end of the head portion on the back face in a width direction in a direction crossing the width direction (usually a direction crossing at or near right angle to the width direction). Usually, the concealing portion is integrated with the main portion along the longitudinal direction by the extrusion molding combined with the main portion. When the pillar molding is attached on the vehicle and employed, the concealing portion is contact with a front window plate face of the vehicle in a part attached along a front pillar portion (a part along the pillar portion), and contact with partially a concave groove (a roof groove) formed on the roof portion to shield the roof groove in a part along the roof portion.
The projection length of the concealing portion is often different between the part along the pillar portion and the other part along the roof portion. For example, the concealing portion projects longer in the part along the pillar portion than the other part along the roof portion, the distal end being contact with a window plate surface. Thereby, the head portion of the main portion is separated away from the window plate surface to the outside of the vehicle, forming a rain water receiving groove between the head portion and the window plate surface for preventing rain water on the window plate surface from flowing across it. On the other hand, the projection length of the concealing portion is shorter in the part along the roof portion than the part along the pillar portion, the distal end of the concealing portion being contact with a roof panel to close the roof groove. A part along the corner portion located between the pillar portion and the roof portion, or its neighborhood, is a start portion of cross sectional change in which the projection length of the concealing portion is changed from the projection length of the roof portion to the projection length of the pillar portion.
Conventionally, this trim member (pillar molding, etc.) is produced in the following way. That is, first of all, the first member formation resin molding material and the second member formation resin molding material are heated and molten, and both the molding materials are extruded simultaneously (coextruded) from the resin extrusion die so that the main portion and the concealing portion may be formed from the molten resin molding material, and cut off in a predetermined length. Thereby, a linear resin extruded molding (composite molding) in which the main portion (first member) and the concealing portion (second member) are integrated along the longitudinal direction is formed. Thereafter, the linear resin extruded molding is thermoldingy bent employing a bender to give a bend shape to the linear resin extruded molding. Then, the thermoldingy bent molding is set in an anneal molding provided with a space of predetermined shape, and left away for several hours to ten and several hours under the temperature condition slightly higher than the heat distortion temperature of the molding material composing the molding material and lower than the melting temperature of the molding material, and the temperature is gradually lowered to the room temperature, after which the resin molding (trim member) is taken out of the annealer. The technique of this type was described in JP-A-2002-347533 below, for example.
In the above manufacturing method for the trim member, first of all, the long composite molding consisting of the first member and the second member integrated in the longitudinal direction is fabricated, and the bending process is performed for this composite molding. Therefore, the composite molding is subject to a compression stress or tensile stress partially in the cross section during the bending process for changing the overall shape of the composite molding, and if the stress is beyond its limit, the cross section may be distorted to unwanted shape. When the cross sectional shape is different between one part of the composite molding and the other part in the longitudinal direction (e.g. when the projection length of the concealing portion is different between one part of the pillar molding and the other part in the longitudinal direction), there is a tendency that such a situation occurs during the bending process. Particularly, in the start portion (corner portion or its neighborhood) of cross sectional change of the concealing portion, a stress is concentrated on the start portion during the bending process, possibly causing a so-called “buckling” phenomenon.